Sure, now we get annoying warnings on every website we visit....

Because the UK intentionally built a loophole into their version of the law.

The actual original cookie law, that was decided on EU level, requires users actually to be able to opt out.

But it was a directive, and so countries could interpret it for local implementations.

The GDPR is a regulation, which means its text is directly law, and it also means it can be a lot stricter.

Not so much a loophole but the UK Information Commissioner certainly adopted a more relaxed approach to enforcement of the requirements of the cookie law compared to other countries.

And the law required prior informed consent to cookies with opt-out not generally being considered to be valid consent.

Talking from experience from a "new" EU country with solid IT scene: the "cookie law" is not enforced at all. Google would be probably the only one theoretically enforcing it (most of websites do show a message because they use Google Analytics), but it would go against Google's interest, so they are not really enforcing it either.